arm64: dts: r8a7796: Add Cortex-A53 PMU node

Enable the performance monitor unit for the Cortex-A53 cores on the
R8A7796 SoC.

Extracted from a patch by Takeshi Kihara in the BSP.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/r8a7796.dtsi

@@ -303,6 +303,18 @@
 					     <&a57_1>;
 		};
 
+		pmu_a53 {
+			compatible = "arm,cortex-a53-pmu";
+			interrupts = <GIC_SPI 84 IRQ_TYPE_LEVEL_HIGH>,
+				     <GIC_SPI 85 IRQ_TYPE_LEVEL_HIGH>,
+				     <GIC_SPI 86 IRQ_TYPE_LEVEL_HIGH>,
+				     <GIC_SPI 87 IRQ_TYPE_LEVEL_HIGH>;
+			interrupt-affinity = <&a53_0>,
+					     <&a53_1>,
+					     <&a53_2>,
+					     <&a53_3>;
+		};
+
 		cpg: clock-controller@e6150000 {
 			compatible = "renesas,r8a7796-cpg-mssr";
 			reg = <0 0xe6150000 0 0x1000>;